The present invention relates generally to refrigeration compressors and more particularly to an improved valve plate assembly for use in such compressors.
Refrigeration compressors of the reciprocating piston type generally incorporate a valve plate containing suction and discharge valves for controlling flow of refrigerant to and from one or more compression chambers. This valve plate is normally clamped between the compressor housing or block and the head. The head will generally include a suction chamber and discharge chamber communicating with the respective suction and discharge valves.
It is generally desirable to minimize the thickness of the valve plate so as to minimize the volume of the discharge passages extending therethrough. This is important because compressed gas remaining in these passages upon completion of the compressor stroke will reexpand thus reducing compressor volumetric efficiency. However, as the valve plate thickness is reduced, its ability to resist pressure and thermal deflections decreases thus giving rise to possible leakage of discharge gas from the compression chamber in the head to the suction chamber or between adjacent cylinders in multiple piston type machines. Thus, in order to insure fluid tight sealing of the valve plate with both the compressor housing and head, it has not been possible to minimize the thickness of the valve plate and has been necessary to utilize larger numbers of closely spaced fasteners to secure the head and valve plate to the housing and/or more complicated head designs to minimize the presence of sealing surfaces on the valve plate in areas where the opposite surface of the valve is not fully supported (i.e. over the cylinder bore for example).
In addition to the above, it is also desirable to insure ample flow area for suction gas to enter the compression chamber. In prior designs multiple elongated reed type suction valves are often utilized being positioned in parallel side by side relationship and secured to the valve plate at the same end thereof. In such an arrangement the maximum valve lift and hence maximum flow area for each valve will be in the same general area. Thus the neighboring suction passages will be competing with each other for suction gas flow. This competition has required that the spacing between such valves be increased thus leaving less area to accommodate discharge ports and associated valving, the length in which the suction valve overlaps the associated port be reduced, trepan valve seats be provided on the valve plate and/or suction port size be increased in order to insure adequate flow to the compression chamber.
The present invention, however, overcomes the above noted difficulties by providing an improved valve plate assembly which incorporates oppositely bowed portions which serve to initially increase the compressive loading on the gaskets in selected areas so as to insure and maintain a fluid tight seal. This arrangement enables the thickness of the valve plate to be reduced thus improving the compressor's volumetric efficiency. Further, greater freedom of design for the head is offered as a result of a reduction in the number of fasteners required for securing the head to the compressor housing. This reduction in the number of required fasteners also reduces the overall cost for parts and assembly labor.
Additionally, the present invention incorporates an improved suction valve assembly wherein a pair of reed type suction valves are secured to the valve plate at opposite ends of the valve members. This arrangement offers substantial improvement in the suction flow characteristics in that the maximum lift of each of the valves and hence maximum flow area therefor is at opposite ends of the two valves. Thus, the competition for flow between the adjacent valves is minimized and thus the spacing therebetween may be reduced, port size can be reduced and valve overlap can be increased.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims taken in conjunction with the accompanying drawings.